1. Field of the Invention
The present invention relates to an apparatus and methods for coupling objects that are displaced from one another. In particular, the present invention relates to an apparatus and methods for coupling objects that are displaced from one another, that is able to adapt to changing operating conditions.
2. Related Art
Designers of composite tubular structures, such as a hose or a tubular, know that positioning the reinforcing fibers or wires is important to the response of the tubular to internal pressure changes. Axially oriented fibers carry axial loads (but limit bending) and circumferential fibers support radial or hoop loads caused by internal pressure. However, helically wound fibers within the construction react and support both axial and hoop loads. The angle of helical fiber lay or lay angle .alpha., relative to the central axis of the tubular, controls the ratio of hoop to axial strength contribution that the respective fiber contributes to the overall strength of the tubular. The conventional tubular designer attempts to limit the global response of the tubular to internal pressure changes by using an assortment of fiber angles and arrangements to prevent an axial length change. Thus, such conventional composite structures are not suitable for use where it is desired to adapt to changing operating conditions, such as in the marine environment.
Typically, when a connector is desired for securing a moving object to a fixed location, the connector is chosen according to its physical properties such as strength and size (i.e. length and diameter). In marine applications, such as tension leg deepwater platform mooring systems and riser assemblies, the vertical connection members that secure the platform to the ocean floor are chosen based on such physical properties. For example, in U.S. Pat. No. 3,934,528, a rope of a particular strength is chosen, the length of which is fixed according to the operating depth of the platform. Once the connection, or mooring, member is installed, there is no way to modify it without complete replacement. This limits the function of the mooring during changing operating conditions such as severe winds and rough seas.
Additionally, there are conventional catenary and taut leg mooring systems which use anchor chains and cables with lengths on the order of six times the water depth. Such systems are expensive to fabricate, install and maintain. Additionally, the transportation of the system to the required location is difficult and costly due to the size and weight of the mooring system materials.
Polyester rope has been used as a lightweight alternative in a taut leg configuration. The taut leg configuration uses seafloor anchors placed such that the taut mooring line has a 45 to 60 degree angle from vertical. This allows shorter lengths of rope to provide the elasticity (stretch) required for mooring. However, the mooring polyester rope is large, typically on the order of twelve inches in diameter. Additionally, in order to install the rope, two support vessels are required. During installation and operation of the taut leg mooring system, constant monitoring of the ropes' tension is required to ensure sound operation and safety. Maintenance of the ropes is difficult. If a rope were to snap, replacement is a costly, time-consuming necessary repair. Maintenance is a constant problem since the ropes are susceptible to external damage and abrasion in the marine environment. Furthermore, the ropes are unable to deploy the seafloor anchors, thus requiring further installation operations and costs.
Some conventional systems use hydraulic cylinders between the `legs` of the platform to dampen lateral movement of the platform. For example, in U.S. Pat. No. 3,983,706, tension cables are used to secure the platform to anchors, but a hydraulic tensioning system provides lateral support.
Connection members are also often used in pump assemblies where a pump is displaced below the operational platform. Such an assembly is described in U.S. Pat. No. 10 5,497,832, assigned to the assignee of the present invention, the entirety of which is incorporated herein by reference. A typical assembly is a downhole plunger piston pump assembly where the rigid "sucker rod" acts as a connection member between the surface platform and the pump. In order to produce the desired pumping action, large machines are utilized to manipulate the rod. Additionally, since the holes in which the pumps are disposed are extremely deep, the long rod is subject to large loads over a great distance, resulting in frequent fatigue failure. In the event that the pump fails, the entire rod assembly must be removed and the pump retrieved.
Thus, there is a need in the art for a simple and inexpensive apparatus to serve as a connector between two objects. Particularly, there is a need in the art for a composite tubular which acts as a connection member that is able to adapt to changing operating conditions. There is also a need in the art for the use of such a connection member in marine mooring systems, riser assemblies, and downhole pump assemblies.